Making your own customer t-shirts is awesome, but it can get a little pricey and excessive if you have to order in bulk. The quality of inkjet transfers isn't exactly ideal, either. Fortunately, Instructables user Matthew Vieke has a great solution that requires just a shirt, a sharpie, and a few other optional items:

Matthew's method involves taking a monotone, high contrast image (or use software to make one that way), print it out, use the tracing box to project the design through the t-shirt, and fill in the blanks with your sharpie. This can be a little time-consuming, but it can also be a relaxing activity that you can do while watching some show or listening to a podcast. In the end you'll have a one-of-a-kind t-shirt that you designed yourself.